Editing Light (section)

===Particle theory===
{{Main|Corpuscular theory of light}}
[[File:PierreGassendi.jpg|thumb|200 px|[[Pierre Gassendi]]]]
[[Pierre Gassendi]] (1592–1655), an atomist, proposed a particle theory of light which was published posthumously in the 1660s. [[Isaac Newton]] studied Gassendi's work at an early age and preferred his view to Descartes's theory of the ''plenum''. He stated in his ''Hypothesis of Light'' of 1675 that light was composed of [[Corpuscularianism|corpuscles]] (particles of matter) which were emitted in all directions from a source. One of Newton's arguments against the wave nature of light was that waves were known to bend around obstacles, while light travelled only in straight lines. He did, however, explain the phenomenon of the [[diffraction]] of light (which had been observed by [[Francesco Maria Grimaldi|Francesco Grimaldi]]) by allowing that a light particle could create a localised wave in the [[Aether (classical element)|aether]].

Newton's theory could be used to predict the [[Reflection (physics)|reflection]] of light, but could only explain [[refraction]] by incorrectly assuming that light accelerated upon entering a denser [[Medium (optics)|medium]] because the [[gravity|gravitational]] pull was greater. Newton published the final version of his theory in his ''[[Opticks]]'' of 1704. His reputation helped the [[particle theory of light]] to hold sway during the eighteenth century. The particle theory of light led [[Pierre-Simon Laplace]] to argue that a body could be so massive that light could not escape from it. In other words, it would become what is now called a [[black hole]]. Laplace withdrew his suggestion later, after a wave theory of light became firmly established as the model for light (as has been explained, neither a particle or wave theory is fully correct). A translation of Newton's essay on light appears in ''The large scale structure of space-time'', by [[Stephen Hawking]] and [[George F. R. Ellis]].

The fact that light could be [[polarized light|polarized]] was for the first time qualitatively explained by Newton using the particle theory. [[Étienne-Louis Malus]] in 1810 created a mathematical particle theory of polarization. [[Jean-Baptiste Biot]] in 1812 showed that this theory explained all known phenomena of light polarization. At that time the polarization was considered as the proof of the particle theory.